It is proposed to study regulation of gene expression in the mammalian testis at the levels of transcriptional and translational control. Using DNA clones prepared against specific nRNAs that are temporally regulated during spermatogenesis, the regulation of these genes will be examined at the levels of transcription, processing of nuclear RNA precursors, movement of the mRNA from nucleus to cytoplasm, and in the cytoplasm. Special efforts will be made to identify specific sequences that encode polypeptides unique to haploid cells to determine when during spermatogenesis the genes are first expressed (in diploid or haploid cells). The repression of gene sequences in the haploid cell and the phenomenon of stored information in the form of "inactive" ribonucleoprotein particles will also be examined. Using established clones for the ribosomal genes, studies will be initiated to answer whether the ribosomal genes are expressed in haploid cells. It is anticipated these studies will answer on a molecular basis whether haploid gene expression occurs, provide a precise answer to how during spermatogenesis the expression of cell type specific gene products are regulated, and reveal critical control points essential for the temporally regulated process of germ cell production.